Modular plug for high speed data transmission

ABSTRACT

A modular plug comprises an insulative housing having a plurality of contacts that have a mating portion and an insulation piercing portion similar to that of conventional modular plugs where the terminals are further provided with capacitor plate portions that are connected to the mating portions via linking portions which cross-over that of an adjacent contact, for at least some of the terminals, in order to provide capacitive coupling between certain contacts to reduce cross-talk.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to connectors provided with means for reducingcross-talk, to enable high speed data transmission.

2. Summary of the Prior Art

There is an increase in demand for cable and connection systems totransmit digital signals at high speeds. As frequency increases,emission of "noise" increases, and this is a particular problem forclosely positioned conductors which are subject to what is calledcross-talk. Beyond a certain transmission frequency, cross-talk becomesunacceptably intense and thus limits the speed of data transmission. Incables, one of the ways of reducing cross-talk is by twisting pairs ofconductors, where one conductor of the pair is for transmitting apositive signal, and the other conductor for transmitting a negativesignal of equal intensity and timing as the positive signal. This iscalled a differential pair due to the nature of the opposed signals inthe pair. Due to the twisting about each other, magnetic and electricalfields emitted from each of the cables cancel each other out and thusnoise emitted from the pair is very low. Such pairs can thus be placedwithin a cable and positioned closely together whilst neverthelesstransmit high speed electrical signals.

One of the problems however occurs at the connection end, where theconductors are connected to terminals within the connector. Terminals ofconnectors are often positioned in juxtaposed parallel relationships,and exhibit more cross-talk than between conductors of the cable. Oneway of reducing cross-talk effects is shown in European PatentPublication No. 583 111 where conductor pairs of a connector arecrossed-over, thus behaving in a similar manner to that of a twistedcable. Crossing-over of contacts in connectors is also shown in U.S.Pat. No. 5,186,647. The latter shows cross-talk reduction in a modularjack, which is a standardized connector widely used intelecommunications and computer data interconnection systems.Standardized modular jacks and corresponding plugs for connectionthereto, were initially designed and used for low speed datatransmission systems, and are thus not necessarily the most effectiveconnection systems for use with high speed data transmission. Due totheir widespread use however, there is a need to improve the datatransmission speed capabilities of modular plug and jack connectorswhilst respecting the standardized interface requirements.

Another means of reducing cross-talk is by judicious capacitive orinductive coupling between conductors of the connector as shown in U.S.Pat. No. 5,326,284. In the latter, the connector (modular jack) ispositioned on a printed circuit board (PCB) having circuit tracesthereon that are arranged in such a manner to couple the conductors bymeans of inductances and capacitances. The purpose of the coupling is toneutralize cross-talk present in the line by further coupling of theconductors to an opposite signal of equal intensity (a differentialsignal). Furthermore, the capacitances and inductances can be adjustedto match the impedance of the connector with that of the cable to reducereflection of signals. Provision of a PCB however requires an extracomponent and increases the cost of the connector assembly. Furthermore,the volume of the connector is also increased. The latter also meansthat some connectors cannot be provided with a PCB, for exampleprovision of a PCB in a modular plug would not be feasible.

G.B.-A-2 271 678 shows a modular jack with terminal contacts having amating portion, an IDC wire connection portion, and capacitance portionsextending integrally via linking portions therebetween. The capacitanceportions are laterally offset from their mating portions and arepositioned over the capacitance plates or the other contacts, for thepurpose of reducing crosstalk between conductor pairs.

U.S. Pat. No. 5,226,835 shows a four conductor patch plug havingterminals with a contact portion and an IDC wire connection portion,adjacent terminals being crossed over at a mid-portion between contactand connection portions thereby adding a controlled half-twist toconductor pairs to reduce crosstalk.

It would be desirable to have an interconnection system that is not onlycost-effective, but also compact and that is for high speed datatransmission, the connector thus having reduced cross-talk andcontrolled impedance. It would also be desirable to provide the latteraspects in a standardized modular plug connector.

It is an object of this invention to provide a compact andcost-effective connector for high speed signal transmission.

It is an object of this invention to provide a standardized modular plugcapable of high speed data transmission.

It is a further object of this invention to provide a compact andcost-effective means for reducing cross-talk in a connector fordifferential signal transmission, and that can be impedance matched witha cable connection thereto.

Objects of this invention have been achieved by providing a connectorcomprising an insulative housing and a plurality of juxtaposed contactsmounted thereon, the contacts having a wire connection portion and amating portion for contact with terminals of a complementary connector,the contacts further comprising plate portions for capacitive couplingbetween contacts. In an advantageous embodiment, the contacts arestamped and formed from sheet metal, and are mounted in a standardizedmodular plug connector. Some of the contacts of the connector maycomprise thin extensions between the contact portions and plateportions, whereby the thin extensions allow a cross-over in the positionof the plate portion with respect to the contact portion such that thecorresponding contact can be capacitively coupled to another contactbeyond the adjacent contact. The mating portion and connection portionsof the contact could be substantially planar, whereby the connectionportion comprises insulation piercing contacts for connection by meansof piercing to conducting strands of insulated conducting wires, and themating portion comprises an arcuate edge of the contact. In the latterdisposition, the capacitance plate portion would extend rearwardly, awayfrom the mating end of the connector, and positionable above wires of acable for connection to the plug, such that a compact arrangement isachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified electrical schema of a capacitance couplingarrangement that can be achieved with this invention;

FIG. 2a and 2b are schematic examples of respective signals transmittedalong a differential pair; and

FIG. 3 is an isometric view of a modular plug according to thisinvention with the contacts shown disassembled from the housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1, eight conductors are represented by the linesnumbered 1-8 of a conductor are shown. These eight conductors belong tofour differential pairs A, B, C and D respectively. Signals aretransmitted by the conductor pairs in a differential manner whereby oneconductor of a pair carries positive voltage signals as illustrated inthe FIG. 2A by the signals S, and the other conductor of the paircarries a signal of equal intensity and timing, but with a negativevoltage with respect to the other conductor. In a twisted pair cable, asthe differential pairs are twisted about each other, emission ofelectromagnetic noise from each of the wires of the pair cancel eachother out thus allowing high speed data transmission.

At the connector, however, the wire ends are straightened and generallypositioned in a juxtaposed manner, an example of which is illustrated inFIG. 1 by the conductors 1-8. Due to this juxtaposed positioning of theconductors, there is unbalanced cross-talk between conductors. As anexample to explain this more clearly, consider the cross-talk betweenconductor 3 and the differential pair A (conductors 1,2). Conductor 3 ispositioned closer to conductor 2 than to conductor 1, and therefore thenoise influence of conductor 2 on conductor 3 is greater than that ofconductor 1 on conductor 3. By placing a capacitance C13 betweenconductors 1 and 3, some of the energy of a signal being transmittedalong conductor 1 is capacitively fed into conductor 3, and if thecapacitance C13 is correctly dimensioned, the additional coupled signalwill cancel out the noise from conductor 2 because of their opposedpotential differences. The influence of the differential pair B(conductors 4,5) on conductor 3 has a similar effect, which is balancedby the capacitance C53 between conductors 3 and 5. With a similarreasoning, positioning of capacitive coupling C46 between conductors 4and 6 and C86 between conductors 6 and 8 balances the influence of pairsB and C respectively on conductor 6. Cross-talk is thus substantiallyreduced between differential pairs A and D, C and D, and B and D. Thedifferential pairs A, B and C are spaced further apart from each other,and are therefore less effected by cross-talk, in particular because themagnetic and electrical fields generated by conductors reducein-strength proportionally to the square of the distance (generallyspeaking).

Referring to FIG. 3, a modular plug connector 10 is shown comprising aninsulative housing 12 and a plurality of stamped and formed contacts 14that are numbered 1-8 corresponding to the layout of FIG. 1. Each of thecontacts 14 has a mating portion 16, a connection portion 18 and acapacitor plate portion 20 connected to the mating portion via a linkingportion 22. The connection portions 18 may be provided with insulationpiercing tips 24 such that the contacts 14 can be pressed onto insulatedconducting wires positioned thereunder. A tool is positioned against anupper edge 23 of the mating portion 16, which is aligned with an uppertool pressure edge 25 of the capacitor plate portion 20, for driving theinsulation piercing tips 24 into the wire conductors positionedtherebelow in conductor receiving cavities of the housing 12. Theinsulation piercing tips 24 pierce through the wire insulation andcontact the inner conducting strands thereof.

The mating and connection portions 16,18 are similar in design to thoseof conventional modular plugs, whereby the modular plug 10 is matable toa conventional modular jack. Electrical connection between the modularplug 10 and spring contacts of the modular jack is effectuated byabutment of the modular jack spring contacts against arcuate contactsurfaces 26 of the mating portion 16. The conducting wires are receivedwithin the housing 10 from a wire receiving end 28 in cavities thatextend upward to proximate the mating end 30 and extending below theinsulation piercing tips 24. Wires of the cable can thus be insertedbelow the contacts 14 which are then depressed for contact to theconducting wires. Each of the contacts 14 is separated from an adjacentcontact by insulative wall portions 32, which laterally support thecontact mating portion 16.

In order to provide the capacitance C13 as shown in FIG. 1, the contactnumber 1 has a linking portion 22 that is oblique such that the plane ofthe plate portion 20 is offset from the plane of the contact portion 16by the distance of the pitch between contacts of the connector. In asimilar manner, the contact number 2 has a capacitor plate portion thatis obliquely offset with respect to the mating portion in the directionof the first contact. The capacitance plate portion 20 of terminal 1 isthus positioned adjacent that of terminal 3 which is generally planar inshape. In order to provide the capacitance C53, plate portion 20 ofterminal 5 is offset from the mating portion 16 and likewise forterminal 4 such that capacitor plate portion of terminal 5 is adjacentthat of terminal 3, and capacitor plate portion of terminal 4 isadjacent that of terminal 6, terminal 6 being similar to that ofterminal 3 in such that it is substantially planar. Terminals 7 and 8have a similar arrangement as that of terminals 1 and 2 respectively.Terminals 1, 4 and 7 have thin linking portions 22 positioned over andacross the linking portions 22 of terminals 2, 5 and 8 respectivelywhich are positioned at a lower height to enable the cross-over of thelinking portions thereof.

In order to achieve the electrical set-up as illustrated in FIG. 1,plate portions of terminals 2 and 7 are not required, however in thisembodiment it is not necessary to move them and as they are similar toother terminals, leaving them on is more cost-effective than removingthem.

As the capacitor plate portions 20 are positioned rearwardly of thecontact mating portion 16 with respect to the mating face 30, a compactarrangement is achieved whilst allowing mating with a standard modularjack: in other words the connector 10 may have a standardized interface.The capacitor plate portions 20 are positioned above the conductingwires and do not increase the space requirements of the connector 10.Furthermore, the contacts are simple unitary stamped and formed partsthat can be easily assembled to the housing 12.

Advantageously therefore, this invention allows a very compact contactarrangement whilst nevertheless providing capacitive coupling ofcontacts for cross-talk reduction and connector-cable impedancematching. The simple stamped and formed unitary contacts arecost-effective to manufacture and assemble, and enable provision ofstandardized modular plug for coupling to a standardized modular jack.

We claim:
 1. A modular plug connector for connection to a complementary modular jack connector, comprising: an insulative housing having a plurality of wire receiving cavities arranged adjacently for receiving conducting wires therein and a plurality of spaced-apart wall portions positioned above and between the wire receiving cavities to define terminal receiving cavities directly above corresponding wire receiving passageways; and, a plurality of juxtaposed stamped and formed terminals positioned in the terminal receiving cavities of the housing, where each terminal has a body with a wire connection portion that includes a insulation piercing tip a mating portion directly above the wire connection portion that includes a connection surface for contact with a corresponding terminal of the complementary modular jack connector and an upper edge for positioning a tool thereagainst for driving the insulation piercing tip into the corresponding conductive wire therebelow, and a capacitance plate portion connected to the mating portion by a linking: portion and extending behind the mating portion, as defined by the connection direction of the modular plug connector and the complementary modular jack connector, where the capacitance plate portion of at least one of the terminals is aligned with and disposed behind the mating portion of another one of the plurality of terminals than the mating portion to which the capacitance plate portion is connected to by way of the linking portion.
 2. The connector of claim 1 wherein the capacitance plate portions are integrally stamped and formed from sheet metal with respective said mating portions.
 3. The connector of claim 1 wherein the capacitance plate portions are positioned above the wire receiving cavities.
 4. The connector of claim 1 wherein the capacitance plate portions are planar.
 5. The connector of claim 1 wherein some of the terminals' linking portions cross over above and are spaced from the linking portions of adjacent terminals.
 6. The connector of claim 1 wherein the capacitance plate portions extend in a juxtaposed parallel manner, from proximate an outer surface of the housing towards the conductor receiving passages of the housing.
 7. The connector of claim 1 wherein the capacitance plate portions have an upper edge aligned with the upper edge of the mating portion. 